Until now, rolls in paper machines and in paper finishing devices except for rolls in which the mantle of the roll is able to move with respect to the axle of the roll, have ordinarily been journalled by means of roller bearings on frame structures of the machine. In particular, in connection with rolls forming a nip, such as calender rolls and soft calender rolls, such roller bearings have caused certain problems, whose solution has required special arrangements. In some cases, it would be desirable to operate soft calenders in particular at linear loads that produce a very small load, even the so-called zero load on roller bearings. This is very problematic in the case of roller bearings because, in the zero load situation, the rolling members of the roller bearing are able to glide considerably with respect to bearing races instead of rolling, with the result that the bearing breaks rather quickly. Heatable rolls, calender rolls in particular, also involve the problem that succeeding in lubrication is a fairly critical factor. In connection with roller bearings, it has been necessary also for this reason to employ special arrangements. Roller bearings additionally involve a vibration problem. The roller bearings in themselves do not have any property that in itself could attenuate such vibration. The structure of the bearing alone sets a certain limit for the speed of rotation, which limit is not permitted by the bearing manufacturer to be exceeded. As already previously mentioned, the rolling accuracy of the bearing is limited. Although all the components in a conventional roll were manufactured as precisely as possible, the defects caused by inaccuracies are summed up in an assembled roll.
Presses also make special demands on journalling of rolls. From the point of view of journalling, extended-nip presses in particular are troublesome because the radial forces acting on bearings in this kind of construction are very high. Special problems of their own are also caused by centre rolls of a press section for the reason that the centre roll generally forms two nips with backup rolls such that the directions of nip planes differ substantially from each other. In that case, it is difficult to determine any actual principal loading direction.
With regard to prior art relating to the journalling with glide bearings, reference is made, for instance, to EP Patent 158 051 which relates to the journalling of a washing drum. The journalling in this arrangement has been provided with glide bearings by means of hydrostatic bearing segments. The mode of journalling in accordance with this publication cannot, however, be used, for instance, in calender rolls that are in nip contact, because the mode of journalling described in this EP publication does not comprise any possibility of radial movement in the bearing itself. Also, the loading of the bearing cannot be changed in any way, and separate spring elements are needed for attenuating vibrations. With respect to prior art, reference is made further to FI Patent application No. 942756 which discloses a bearing for a heated roll. This mode of journalling also involves the drawback that there exists no possibility of radial displacement, because at least one hydrostatic bearing segment of the glide bearing arrangement is, in the radial direction, completely fixed and stationary with respect to a frame structure, and, thus, it is not possible to displace the roll carried by means of said bearing, for instance, in the direction of the nip plane.